Fuel injection system for internal combustion engines



Oct. 8, 1935. B. WALKER 2,016,619

FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed Aug. 11,1930 INVENTOR.

A TTORNE YS.

Patented Oct. 8, 1935 UNITED STATES PATENT orrics FUEL INJECTION SYSTEMFOR INTERNAL COMBUSTION ENGINES Brooks Walker, Piedmont, Calif.

- Application August 11, 1930, Serial No. 474,412

3 Claims.

vary as the speed changes, but in which there is no appreciable changein head per cycle.

It is the principal object of the present invention to provide a linepressure fuel system for internal combustion engines by means of which ametering of .the fuel will be maintained throughout a predeterminedrange of engine speeds.

In carrying out this object into practice, I provide in conjunction witha line pressure system, an apparatus capable of varying the fuel linepressure in such a manner as to maintain the velocity of injectionsubstantially proportional to engine speed.

To accomplish this result the differential pressure between the fuelpressure and the pressure of the compressed charge within the cylindermust vary approximately as the square of the engine speed. Thisconstruction is such as to accomplish the desired result without thenecessity of governors, electric devices, or-other speed sensitive unitseffecting the control.

The regulation of the pressure control causes thevel ocity of dischargeat the nozzle to vary approximately in direct proportion to the enginespeed, which results in the injection of a substantially constant chargeof fuel per cycle throughout a predetermined range of engine speed, andconsequently will cause the engine to deliver a substantially constantmaximum torque under varying speed'changes without the injection of anexcess of fuel at reduced speeds. This characteristicis desirable inengines operating under widely varying load conditions, such as isrequired in the propelling of vehicles, in which the engine, forexample, may be can'ying full torque at high speed when the vehicleencounters an increase in grade, which will cause the motor speed to bedecreased. During this change of speed it is desirable to maintain themaximum principle, in which the air charge per cycle is, a relativeconstant, regardless of speed or throttle position, the fuel charge mustalso be maintained a constant per cycle.

This invention is based largely on the assumptionthat the displacementof the fuel pump is constant per revolution, and that it is drivenbyengine means. The invention resides in the combination of a fuel linesystem and a by-pass of the fixed area type irrespective of pressurechanges, which combination makes the discharge of the injection valvesinto the cylinders plus the discharge of this valve equal to thedisplacement of the fuel pump, at full speed and at full load, and willconsequently maintain the injection quantity per injection a constant atreduced speeds.

The invention is exemplified in the following description andillustrated by way of example in the accompanying drawing, in which:

Fig. 1 is a schematic view disclosing the line pressure being controlledby a rigid type by-pass.

Fig. 2 is a schematic view of an alternative type of by-pass control.

Referring to the accompanying drawing. and particularly to Fig. 1, ourapparatus discloses the usual reservoir III, which is connected by asupply line I l, to the intake port of a fuel pump l2. Thedi'scharge'point of the pump l2, isconnected by a delivery pipe line H,to the fuel in- 30,

ed by-pass valve assembly 20 is interposed between the delivery line andthe by-pass line. The by-pass valve 2|, is also interposed between thedelivery line H and the discharge l9. This valve 2|, is of the rigidtype needle valve construction providing a fixed area orifice,regardless of pressure at' a given setting. I

Theby-pass, 20 is of the spring loaded type, manually adjustable tolimit the maximum pressure obtainable in the line and the maximum enginespeed. During the operation of the engine,

the pump l2, which is drivenat some multiple of the engine speed,delivers approximately a fixed quantity of oil per revolution against apressure of 5,000 pounds per square inch, for example, at

full speed and full throttle. The spring loaded valve, 20 may be set for5,500 pounds as a safety Iii device, and the needle valve adjusted todischarge a sufllcient quantity to lower the pressure to the desired5.000 pounds.

The discharge of the pump is balanced by the discharge of the injectionvalves at full throttle (which are open for a given crank angle, and aretherefore, open for a given percentage of the time, regardless of theengine speed, at full throttle) plus the discharge of the by-pass valve2|. The injection valves being of the usual type with injection orificesbelow the valve seat constituting a fixed area orifice, which orifice asstated,

is open for a given percentage of the time at full throttle at allspeeds. The injection valve operating for a fixed percentage of the timeas described, and the fixed area by-pass cooperate to discharge the pumpdisplacement, which varies as to the engine speed.

As disclosed herein the by-pass discharge plus the injection dischargeinto the cylinders has been made equal to the pump displacement so thatin the event that the motor speed is reduced by half, due to exteriortorque requirements the pump will discharge half as much fuel in thesame time period and there will be half as much fuel discharged throughthe nozzles into the cylinders in the same time, but since there arehalf as many injections of twice the duration each, each injection willdischarge the same quantity as at the high speed. With this valve fixed,the discharge characteristic will only be as described when the throttleis wide. open. When the crank angle of injection duration is reduced toeffect throttling, the displacement of the pump will become greater thanthe displacement of the injection valves it, plus the needle valves 2 I,at the pressure persisting at full throttle operation and the resultingpressure may rise to the value where the spring loaded valve 20 willcontrol it.

This metering characteristic may not be satisfactory for all cases whereequal metering per injection is desired at reduced throttle operationthroughout the speed range. For this purpose I have provided in Fig. 2an alternative construction for the valve 2|. In Fig. 2 the valve 22 isprovided with a valve stem 23, on which is mounted a control arm 24,connected to the throttle control 25 by means of a suitable linkage 26.The valve stem 23 is provided with threads or other suitable meansadapted to engage threads in the housing so that a partial rotation ofthe stem will vary the area of the orifice. The connection between thethrottle control 25 and the valve control 24 is such as to provide anincrease in the rigid discharge area irrespective of fluid pressurechanges as the crank angle of injection duration decreases, and viceversa, to approximately re-establish equal metering at reduced throttleoperation for a given speed range.

In the construction shown in Figure 2 the area of the by-pass valve isincreased to prevent an increase of fuel pressure where the angle ofinjection duration is reduced for throttling only, this results in asingle reduction of injecting volme only. The reduction of angle ofinjection duration, and not pressure necessarily, results in a reduceddischarge volume per injection, thus giving a reliable throttle.

As a method of illustration, I have shown the well known wedge method ofvarying the crank angle of injection duration, in which the cam 30operates a tappet 3|, a movable wedge 35, a

tappet :2, a push rod 31,8. rocker arm a, and r While I have disclosedspecific types of apparatus for practicing the invention, it is to beunderstood thatmy invention can be practiced by various types ofapparatus within the scope of 1 the appended'clalms.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. In a circuit for a fuel injection system of the rail pressure type,the combination of a fuel injection valve, mechanism for operating saidvalve, a throttle control for regulating the crank angle of discharge ofsaid valve, said mechanism adapted to open said valve for a constantcrank angle of duration at a given throttle setting, a fuel pump forsupplying fuel under pressure to the pressure rail, a bypass valvecontinuously connected to said pressure rail, exterior means foradjusting the area of said bypass, the area remaining fixed for anygiven adjustment regardless of engine speed, an interconnection betweensaid exterior means and said throttle control so as to vary the bypassadjustment and the crank angle of discharge simultaneously.

2. In a circuit for a fuel injection system of the rail pressure type,the combination 01 a fuel injection valve, mechanism for operating saidvalve, a throttle control for regulating the crank angle of discharge ofsaid valve, said mechanism adapted to open said valve for a constantcrank angle of duration at a given throttle setting, a fuel pump forsupplying fuel under pressure to the pressure rail, a bypass valvecontinuously connected to said pressure rail, exterior means foradjusting the area of said bypass, the area remaining fixed for anygiven adjustment regardless of engine speed, an interconnection betweensaid exterior means and said throttle control so as to increase thebypass area as the crank angle of injection duration is reduced at agiven engine speed.

3. In a circuit for a fuel injection system of the rail pressure type,the combination of a' fuel injection valve, mechanism for operating saidvalve, a throttle control for regulating the crank angle of discharge ofsaid valve, said mechanism adapted to open said valve for a constantcrank angle of duration at a given throttle setting, a fuel pump forsupplying fuel under pressure to the pressure rail, a bypass valvecontinuously connected to said pressure rail, exterior means foradjusting the area of said bypass, the area remaining fixed for anygiven adjustment regardless of engine speed, 'an interconnection betweensaid exterior means and said throttle control so as to increase thebypass area as the crank angle of injection duration is reduced at agiven engine speed to maintain substantially the same fuel pressureduring changed throttle settings at one engine speed and inherentlyproduce substantially constant individual fuel discharges over a widerange of engine speeds at one throttle setting. BROOKS WALKER.

Patent No. 2,016,619 Granted October 8, 1935 BROOKS WALKER The aboveentitled patent was extended J nly 24, 1951, under the provisions of theact of June 30, 1950, for 6 years and 214 days from the expiration ofthe original term thereof.

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